Key result
Increasing exercise workload while maintaining a constant atrial pacing rate resulted in a pronounced shortening of the A-R interval in patients with sinus node dysfunction (P<0.0001).
Why the study?
Does the A-R interval change predictably during exercise in patients with pacemakers for severe atrial bradycardia and intact AV conduction?
Does the A-R interval change predictably during exercise in patients with pacemakers for severe atrial bradycardia and intact AV conduction?
The A-R interval shortens predictably during exercise in patients with sinus node dysfunction and intact AV conduction, suggesting it could be used as a physiological indicator for rate-adaptive atrial pacing.
Answers are grounded in this paper and cite their sources.
May support A-R interval as exercise sensor for rate-adaptive atrial pacing; hypothesis-generating pending larger trials.
We investigated the possibility to use the interval from an atrial stimulus to the ventricular R wave (A-R interval) as an indicator of physical stress, in 16 patients with pacemakers implanted for severe atrial bradycardia but with intact AV conduction. The A-R interval was studied during incremental atrial pacing at rest and during exercise with a constant workload. In addition, the atrial pacing rate was kept constant just above spontaneous sinus rate and the dynamics of the A-R interval were studied during exercise with a low constant workload and during a maximal exercise test with increasing workload. Incremental atrial pacing prolonged the A-R interval and this response was blunted during exercise (P less than 0.003). Atrial pacing at a constant rate and during a constant workload resulted in an almost direct shortening of the A-R interval. When the workload was increased but the atrial rate kept constant, a pronounced shortening of the A-R interval was noted (P less than 0.0001). It is concluded that changes of the A-R interval during different kinds of exercise were prompt and predictable in patients with sinus node dysfunction but intact AV conduction. In these patients the shortening of the A-R interval during exercise may be a suitable indicator for rate adaptive atrial pacing.
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Ruiter et al. (1990) studied Severe atrial bradycardia with intact AV conduction (n=16). Exercise with constant atrial pacing rate vs. Rest or low constant workload was evaluated on A-R interval shortening (p=<0.0001). Increasing exercise workload while maintaining a constant atrial pacing rate resulted in a pronounced shortening of the A-R interval in patients with sinus node dysfunction (P<0.0001).
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